Positive displacement pumps such as lobe pumps have been in existence for a number of years. They are used in a variety of industries such as the food industry, beverage industry, pharmaceutical industry, paper industry and other industries. They are a particularly attractive option in many industries as they can be highly efficient, reliable, resistant to corrosion and have excellent sanitary properties. They traditionally provide excellent clean in place (CIP) characteristics for such applications where the pumps are routinely taken apart and cleaned as it relates to cleaning the cavity, rotors and associated components.
Lobe pumps often offer continuous, intermittent or reversible flow. Their construction allows for flow to be relatively independent of changes in pressure. Output can therefore be relatively constant and continuous.
Lobe pumps operate by providing at least two rotors which are supported by parallel shafts: a drive shaft and a lay shaft. The lay shaft is driven by gearing of the drive shaft to the lay shaft in a gear box which is usually integrally connected to the casing having a rotor housing. Seals prevent an exchange of fluid from the rotor housing into the bearing housing. As the shafts turn, they are operably coupled to the rotors causing the rotors to turn. The rotors have cooperating lobes.
As the lobes mesh with one another, they create an expanding volume on the inlet side of the pump. Liquid or solid flows into the cavity and is trapped by the lobes as they rotate. The material travels around the interior of the casing and the pockets between the lobes and the casing while not passing between the lobes. Finally, the meshing of the lobes forces the liquid material out the outlet port under pressure. Various improvements have occurred over the years with lobe pumps. U.S. Pat. No. 6,053,717 shows wiper inserts which extend radially from the lobes.
U.S. Pat. No. 5,567,140 shows another improvement. In this design, a pump chamber is defined in the pump housing by opposed front and rear end walls which are perpendicular to the axes of the rotors and by arcuate side walls. The rotors are believed to make sealing contact with these surfaces and they gradually wear out thereby reducing the tightness of the seal and thus the pumping efficiency of the rotary lobe pump. In an effort to provide better seals, the rear end wall construction includes two removable wear plates. The arcuate side walls are also provided with removable wear plates. Although this is certainly one method to address wear, the applicant believes there is an additional and/or improved methods of addressing wear and providing improved positive displacement pumps.